And I found that the error seems happen jboss-5.1.0.GA on Windows Server 2003 R2 , We had tried ,the jboss-5.1.0.GA Server on Windows7 works fine to us. We had use the same source code ,workflows and Database on our testing.
BTW we also found that the JDK version aslo a factor on this problem,on the jboss-5.1.0.GA on Windows Server 2003 R2 ,the different JDK version will have different error rate. under the JDK1.6.0_13, we have nealy 10% error, and under JDK1.6.0_30, we only got less than 5% error in the same stressing.